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MC145050DW 参数 Datasheet PDF下载

MC145050DW图片预览
型号: MC145050DW
PDF下载: 下载PDF文件 查看货源
内容描述: 10位A / D转换器,串行接口 - CMOS [10-Bit A/D Converter with Serial Interface - CMOS]
分类和应用: 转换器
文件页数/大小: 15 页 / 555 K
品牌: LANSDALE [ LANSDALE SEMICONDUCTOR INC. ]
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ML145050, ML145051  
LANSDALE Semiconductor, Inc.  
PIN DESCRIPTIONS  
D
out  
Serial Data Output of the A/D Conversion Result(Pin 16)  
DIGITAL INPUTS AND OUTPUT  
This output is in the high-impedance state when CS is in  
active high. When the chip recognizes a valid active low on  
The various serial bit-stream formats for the ML145050/51  
are illustrated in the timing diagrams of Figures 9 through 14.  
Table 1 assists in selection of the appropriate diagram. Note  
that the ADCs accept 16 clocks which makes them SPI (Serial  
Peripheral Interface) compatible.  
CS, D  
is taken out of the high-impedance state and is driv-  
out  
en with the MSB of the previous conversion result. (For the-  
first transfer after power-up, data on D is undefined for the  
out  
changes to the second most  
entire transfer.) The value on D  
out  
significant result bit upon the first falling edge of SCLK. The  
remaining result bits are shifted out in order, with the LSB  
Table 1. Timing Diagram Selection  
appearing on D  
upon the ninth falling edge of SCLK. Note  
out  
that the order of the transfer is MSB to LSB. Upon the 10th  
falling edge of SCLK, D is immediately driven low (if  
No. of Clocks in Using  
Serial Transfer  
Interval  
Figure  
No.  
Serial Transfer  
CS  
out  
10  
10  
Yes  
No  
Don't Care  
Don't Care  
Shorter than Conversion  
Shorter than Conversion  
Longer than Conversion  
Longer than Conversion  
9
allowed by CS) so that transfers of more than 10 SCLKs read  
zeroes as the unused LSBs.  
When CS is held active low between transfers, D  
en from a low level to the MSB of the conversion result for  
three cases: Case 1 – upon the 16th SCLK falling edge if the  
transfer is longer than the conversion time (Figure 14); Case 2  
– upon completion of a conversion for a 16-bit transfer interval  
shorter than the conversion (Figure 12); Case 3– upon comple-  
tion of a conversion for a 10-bit transfer (Figure 10).  
10  
11  
12  
13  
14  
11 to 16  
16  
Yes  
No  
is driv-  
out  
11 to 16  
16  
Yes  
No  
CS  
Active-Low Chip Select Input (Pin 15)  
Chip select initializes the chip to perform conversions and  
provides 3-state control of the data output pin (D ). While  
out  
Din  
inactive high, CS forces D  
to the high-impedance state and  
out  
Serial Data Input (Pin 17)  
disables the data input (D ) and serial clock (SCLK) pins. A  
in  
The four-bit serial input stream begins with the MSB of the  
analog mux address (or the user test mode) that is to be con-  
verted next. The address is shifted in on the first four rising  
edges of SCLK. After the four mux address bits have been  
received, the data on D is ignored for the remainder of the  
present serial transfer. See Table 2 in Applications Information.  
high-to-low transition on CS resets the serial dataport and syn-  
chronizes it to the MPU data stream. CS can remain active  
during the conversion cycle and can stay in the active low state  
for multiple serial transfers or CS can be in active high after  
each transfer. If CS is kept active low between transfers, the  
length of each transfer is limited to either 10 or 16 SCLK  
cycles. If CS is in the inactive high state between transfers,  
each transfer can be anywhere from 10 to16 SCLK cycles  
long. See the SCLK pin description for a more detailed discus-  
sion of these requirements.  
in  
SCLK  
Serial Data Clock (Pin 18)  
This clock input drives the internal I/O state machine to per-  
On the ML145050/51 spurious chip selects caused by system form three major functions: (1) drives the data shift registers to  
noise are minimized by the internal circuitry.  
simultaneously shift in the next mux address from the D pin  
in  
Any transitions on the ML145050 CS pin are recognized as  
valid only if the level is maintained for a setup time plus two  
falling edges of ADCLK after the transition.  
and shift out the previous conversion result on the D  
pin,  
out  
(2) begins sampling the analog voltage onto the RCDAC as  
soon as the new mux address is available, and (3) transfers  
control to the A/D conversion state machine (driven by  
Transitions on the ML145051 CS pin are recognized as valid  
only if the level is maintained for about 2 ms after the transition. ADCLK) after the last bit of the previous conversion result has  
been shifted out on the D pin.  
out  
NOTE  
The serial data shift registers are completely static, allowing  
SCLK rates down to the DC. There are some cases, however,  
that require a minimum SCLK frequency as discussed later in  
this section. SCLK need not be synchronous to ADCLK. At  
least ten SCLK cycles are required for each simultaneous data  
transfer. If the 16-bit format is used, SCLK can be one contin-  
uous 16-bit stream or two intermittent 8-bit streams. After the  
serial port has been initiated to perform a serial transfer*, the  
new mux address is shifted in on the first  
If CS is inactive high after the 10th SCLK cycle-  
and then goes active low before the A/D conversion  
is complete, the conversion is aborted and the chip  
enters the initial state, ready for another serial trans-  
fer/conversion sequence. At this point, the output  
data register contains the result from the conversion  
before the aborted conversion. Note that the last  
step of the A/D conversion sequence is to update the  
output data register with the result. Therefore, if CS  
goes active low in an attempt to abort the conver-  
sion too close to the end of the conversion  
*The serial port can be initiated in three ways: (1) a recog-  
nized CS falling edge, (2) the end of an A/D conversion if the  
port is perform-ing either a 10-bit or a 16-bit “shorter-than-  
conversion” transfer with CS active low between transfers,  
and (3) the 16th falling edge of SCLK if the port is perform-  
ing 16-bit “longer-than-conversion” transfers with CS active  
low between transfers.  
sequence, the result register may be corrupted and  
the chip could be thrown out of sync with the  
processor until CS is toggled again (refer to the AC  
Electrical Characteristics in the spec tables).  
Page 6 of 15  
www.lansdale.com  
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